The document discusses synchronous motors used to drive textile and paper mill equipment. It describes different types of synchronous motors including wound field, permanent magnet, synchronous reluctance, and hysteresis motors. It explains that synchronous motors can operate in an adjustable frequency control mode called self-controlled mode, where the supply frequency is controlled by an inverter receiving signals from a frequency controlled oscillator. In this mode, the motor exhibits constant torque behavior up to base speed and flux weakening at higher speeds, with fast transient response similar to a DC motor but smaller rotor inertia.

1. synchronous motor
drive

2.  Wound field motor
(a)cylindrical rotor wound field motor
(b) salient pole rotor wound field motor
 Permanent magnet motor
 Synchronous reluctance motor
 Hysteresis motor

3.  Modes of adjustable frequency control
(i) Open loop volts/HZ control (or) separate cotrolled
(or) true synchronous mode
(ii)self-controlled mode

6.  Fiber spinning
 Textile and paper mill

7.  Supply Frequency to the synchronous motor is
controlled from the inverter which receives its firing
pulses from a frequency controlled oscillator.
 The machine will exhibits conventional behavior.
 Up to base speed the motor operates at constant
torque and above base speed are obtained by
clamping the voltage at rated voltage. Frequency can
be increased and the motor operates in flux
weakening region

8.  Control can modify the angle between the flux
phasors
 Because of self-control, machine does not show any
stability or hunting problem of traditional
synchronous machine
 The transient response is fast – similar to dc machine
 The rotor inertia is smaller than dc machine with high
energy magnet

10.  Commutation of the converter feeding the motor is controlled
through the rotor position information from a shaft encoder.
 Under over excitation the motor voltages can be employed to
commutate the thyristors at the inverter. Now the inverter
becomes simple. But at low speeds commutation assistance is
required.
 Rotor position is sensed and the firing signals to the devices
are synchronized to the motor position.
 For every 600 rotation of the rotor a new device in the
sequence is fired

21.  A Synchronous motor in self controlled mode is
called “commutator less Dc motor”.